Intelligibility of children's speech in digitized speech

The current investigation examined the intelligibility of digitized speech recorded from typically developing child speakers, ages 4, 5, 6, and 7 years, and reproduced on an augmentative and alternative communication (AAC) device with digitized speech output. The study used a between group design. Forty adults were asked to transcribe 120 words spoken by child speakers in one of the age groups, and presented on an AAC device with digitized speech output. The dependent variable was intelligibility (percent of words correctly identified) of the children's speech. Overall, the intelligibility of children's speech increases with the age of the child speaker. However, there was a lot of individual variation in the intelligibility of children's voices. There was no clear cut-off age, although the speech of some young children may not be sufficiently intelligible on an AAC device that uses digitized speech. Clinicians and parents choosing child speakers for AAC devices with digitized speech are cautioned to carefully consider the speakers used for recording digitized speech output and the characteristics of the speech of the individual speaker. Future research directions are discussed.